When you arrive at Kataragama vendors will attempt to sell you offerings of fruit as part of the Hindu ceremonies, if you have a driver/guide he will know what to do with it but if you are on your own it can be a little confusing. If you want to take part just follow the crowd and do what they do, the Hindu Priest will take a little of the fruit and you can eat the rest.
Visit during festival times in the months of July/August and you would see thousands of pilgrims practice self-mortification in fulfillment of vows to the Gods. Devotees fast, meditate and pray; bathe in the Menik Ganga (River) and then worship at the Maha Devale before facing their ordeal. This includes the famous "fire walking" - when believers walk on a bed of burning, live coal